From the past, in digital television broadcasts, for example, there is a multi-view technique of displaying a plurality of video content screens on one screen displayed on a display connected to a receiver that receives videos (see, for example, Patent Document 1).
In this technique, a transmission-side transmission apparatus that transmits videos transmits size-reduced video signals for service that correspond to a plurality of channels. The receiver causes the display to display a multi-screen (13) in which the video signals for service are arranged longitudinally and laterally. A user uses a remote controller or the like to select one of the plurality of videos by focus display while looking at the multi-screen (13). Accordingly, the user can view a program of the selected video.
On the other hand, in recent years, an HDMI (High Definition Multimedia Interface) (registered trademark (hereinafter, referred to as R)) is becoming popular as a communication interface for transmitting uncompressed (baseband) video data and audio data associated with the video at high speed. For example, an HDMI® is capable of transmitting high-image-quality video data from a DVD (Digital Versatile Disc) recorder, a set-top box, and other AV (Audio Visual) sources to a television receiver, a projector, and other displays.
The HDMI® includes a TMDS (Transition Minimized Differential Signaling) channel that unidirectionally transmits video data and audio data from an HDMI source to an HDMI sink at high speed. In the HDMI, a CEC line (Consumer Electronics Control Line) and the like for bidirectional communication between the HDMI® source and the HDMI® sink is defined in the HDMI specifications.    Patent Document 1: Japanese Patent Application Laid-open No. 2002-281406 (paragraph [0032], FIGS. 5(A) to (C))